Molybdenum flame spray wire and process



y 1969 H. s. INGHAM, JR. ET AL 3,455,508

MOLYBDENUM FLAME SPRAY WIRE AND PROCESS Filed June 5, 1966 FIG. lb.

FIG. 2.

FIG. 21).

R J .S I M 0A H G m V NS l R E B R E H HERBERT S. INGHAM. SR.

ATTORNEYS.

United States Patent 3,455,508 MOLYBDENUM FLAME SPRAY WIRE AND PROCESS Herbert S. Ingham, Jr., Northport, and Herbert S. Ingham, Sn, Glenhead, N.Y., assignors to Metco Iuc., Westbury, N.Y., a corporation of New Jersey Filed June 3, 1966, Ser. No. 555,192 Int. Cl. B05b 1/02 US. Cl. 239-13 Claims ABSTRACT OF THE DISCLOSURE A molybdenum flame spray Wire having roughened abrasive surface areas with sharp projections, intervals not exceeding about 1 foots distance therebetween; the roughened abrasive surface areas preventing jamming and sticking as the wire is passed through the flame spray gun. The roughened surface areas may extend over the entire surface of the wire, giving the wire a surface roughness in excess of at least 50 and preferably at least 200 microinches RMS.

This invention relate-s to an improved molybdenum flame spray wire.

It is well known and conventional to effect flame spraying with the use of a flame spray material in the form of a wire utilizing a wire-type flame spray gun (the term wire being used generically to designate a rod or wire).

With the advent of the discovery that sprayed molybdenum would bond teu'aciously to a substrate so that the initial spraying of molybdenum could be used as a bonding coat for subsequently applied flame sprayed layers (see US. Patents Nos. 2,588,421 and 2,588,422), the flame spraying of molybdenum wire has become very common and molybdenum flame-spray wire has been sold and sprayed in ever increasing quantities.

As compared with other conventional flame spray wires molybdenum flame spray wire has shown the unique disadvantage of tending to stick and jam in the nozzle of the flame spray gun after a given period of spraying.

This sticking and jamming problem occurs even though the surface of the wire may be smooth and uniform and the diameter of the Wire has been maintained uniform within close tolerances. Furthermore, lubrication has proven no solution to this problem.

In spite of the fact that continuous efforts have been made to solve this problem, as for example by design improvements of the spray gun nozzle and air cap, and while the problem has been somewhat reduced by these improvements, the same has never been solved.

One object of this invention is a novel molybdenum flame spray wire which does not have this tendency to stick or jam in the flame spray gun nozzle. This and still further objects will become apparent from the following description read in conjunction with the drawings in which:

FIG. 1 is a perspective view showing an embodiment of a piece of molybdenum flame spray wire in accordance with the invention,

FIG. 1b shows the surface of the Wire of FIG. 1 on an enlarged scale,

FIG. 2 is a perspective view showing a further embodiment of the invention, and

FIG. 2b shows a portion of the surface of FIG. 2 on an enlarged scale.

In accordance with the invention, we have surprisingly discovered that, if the molybdenum flame spray wire is provided with roughened abrasive surface areas having sharp projections and extending around the circumference 3,455,508 Patented July 15, 1969 of the wire at intervals not exceeding a foots distance therebetween, the tendency towards sticking and jamming is avoided.

In accordance with one preferred embodiment as shown in FIG. 1, the entire surface of the molybdenum flame spray wire is roughened to provide a surface finish of at least 50 and preferably at least 200 microinches RMS. The roughening may be effected in any known or desired manner, but is preferably effected by grit blasting in the same manner as is conventionally used for preparing a surface for flame spraying. Most preferably the grit blasting is effected With an angular chilled iron grit having a size between G25 to G40 (SAE mesh size). Coarse sand or other conventional grits of suflicient hardness to roughen molybdenum may be used. Examples of such grits include silicon carbide, aluminum oxide, silica, etc.

In place of grit blasting, any other known or conventional mode of roughening a metal surface so as to provide a roughened abrasive surface with sharp projections may be used. This may, for example, include a mechanical roughening, such as knurling, etching, or the like. The roughened surface must be sufliciently roughened so that its initial abrasive characteristics have the appearance of at least a 100 grit sandpaper.

It is not necessry that the entire surface of the wire be roughened and within the broadest scope of the invention intermittent roughened areas extending about the circumference of the wire will suffice. These roughened areas should not be further spaced at more than about a foot apart, and preferably should be provided with a spacing of less than 6 inches and most preferably about 1 inch the'rebetween. The size of the roughened areas is not critical and may be in the form of a single sharp shoulder or projection as is shown in FIG. 2.

In all other respects the wire is in the form of the conventional well known molybdenum flame spray wires which normally range from about 15 gauge to diameter. While the wire is normally pure molybdenum, the invention is also applicable to molybdenum alloy flame spray Wires which have a jamming tendency.

The initial wire prior to the roughening should be of the conventional size and though the roughening generally increases the measured diameter of the wire because of peaks in the roughness, thus reducing the clear-ance in the novel bushing, nevertheless, the tendency to jam is avoided.

Aside from elimination of the sticking and jamming tendency, the roughened wire in accordance with the invention shows sprayability equivalent to non-roughened wire.

The roughening in accordance with the invention should not be such that the surface finish exceeds about 500 microinches RMS.

In order to illustrate the effectiveness of the invention, the following tests were conducted.

Test 1 A conventional pure molybdenum wire sold under the tradename Metco Sprabond was sprayed in a conventional wire type flame spray gun (Metco K gun). After 37 minutes of spraying, the wire feed became erratic, showing indications of stoppage, and complete jamming occurred after about 44 minutes.

Test 2 Metco Sprabond molybdenum wire from the same stock as the wire used in Test 1, was initially surface-roughened by grit blasting with angular chilled iron grit consists of a 50%50% mixture of SAE sizes G25 and G40, at pounds pressure so that the wire was roughened to provide an abrasive surface finish with sharp projections having a surface finish of about 200 microinches RMS. This wire was sprayed under the identical conditions and with the identical equipment as described in Test 1. No tendency toward stoppage or jamming occurred even after prolonged spraying many times longer than that which caused the jamming in Test 1.

Various types of molybdenum flame spray wire provided with continuous and intermittent roughened surface areas in accordance with the invention were sprayed under various conditions and did not show the tendency toward jamming which is normally encountered in connection with the smooth finished Wire. Furthermore, the roughened wire in accordance with the invention did not cause increased wear of the gun or the nozzle.

While the invention has been described in detail with reference to certain specific embodiments, various changes and modifications which fall within the spirit of the invention will become apparent to the skilled artisan. The invention is therefore only intended to he limited by the appended claims or their equivalents wherein we have endeavored to claim all inherent novelty.

We claim:

1. A molybdenum flame spray wire having roughened abrasive surface areas with sharp projections and a surface roughness in excess of 50 microinches RMS at intervals not exceeding about a foots distance therebetween.

2. Molybdenum flame spray wire according to claim 1 in which said roughened surface areas extend substantially over the entire surface of the wire.

3. Molybdenum flame spray wire according to claim 2 in which said roughened surface is a grit blasted surface.

4. Molybdenum flame spray wire according to claim 3 in which said wire has a surface finish of about 200 microinches.

5. Molybdenum flame spray wire according to claim 1 in which said roughened abrasive surface areas are in the form of sharp shoulders circumventing the wire.

6. In the process for flame spraying a molybdenum flame spray wire in which the wire is passed through a wire-type flame spray gun, the improvement for preventing jamming and sticking of the wire which comprises effecting the flame spraying utilizing a molybdenum flame spray wire having roughened abrasive surface areas with sharp projections and a surface roughness in excess of 50 microinches RMS at intervals not exceeding about a foots distance therebetween.

7. Process according to claim 6 in which said flame spray wire is a wire in which said roughened surface areas extend substantially over the entire surface of the wire.

8. Process according to claim 7 in which said flame spray Wire is a wire in which said roughened surface is a grit blasted surface.

9. Process according to claim 8 in which said Wire has a surface finish of about 200 microinches.

10. Process according to claim 6 in which said roughened abrasive surface areas are in the form of sharp shoulders circumventing the wire.

References Cited UNITED STATES PATENTS 2,588,421 3/1952 Shepard 1l771 2,905,512 9/1959 Anderson 117-105 X 3,017,119 1/1962 Gibson 117-105 X L. DEWAYNE RUTLEDGE, Primary Examiner E. L. WEISE, Assistant Examiner US. Cl. X.R. 

